My suggestions to breakthrough in one hit using GVG (thanks jbark!): 

Load a fresh bowl of at least 25 mgs.  Have a second dose pre-prepared and on hand, in a form/carrier that makes it easy to load into the pipe if you are tripping hard.

Begin by taking a very slow hit until you see the GVG fill with white vapor.  Then take a quick moment to exhale all the air in your lungs, light again and take the biggest, SLOWEST hit you possibly can.  The slower you go the heavier/thicker/more potent that vapor will become.

If this does not get you where you want to go, repeat this procedure as soon as you can, that is as soon as your trance breaks and you can control your hands and load the pipe.

Peace & Love